This invention relates to a liquid container and a cartridge including the liquid container, a printing apparatus using the cartridge and a liquid-discharge printing apparatus, and more particularly, to a liquid container to supply ink to a printhead which performs printing in accordance with an ink-jet method, a cartridge including the liquid container, a printing apparatus using the cartridge and a liquid-discharge printing apparatus.
According to the conventionally known devices for detecting existence/absence of residual ink in an ink tank containing ink, electrodes are provided in the ink tank and electric conductivity between the electrodes is measured, or a discharged ink droplet is optically detected. Generally, as a method of using electrodes complicates the structure of the ink tank, means for optically detecting existence/absence of residual ink is usually employed.
Particularly, an ink-jet printing apparatus for performing printing by discharging ink contained in an ink tank generally comprises a printhead which discharges ink to a print medium, an ink tank containing ink to be supplied to the printhead, conveyance means for conveying the print medium and control means for controlling printing operation, scanning operation and the like of the printhead. In this apparatus, if the amount of residual ink in the ink tank is less than a predetermined amount, ink supplied to the printhead becomes insufficient and may cause discharge failure. For this reason, the apparatus further comprises a device and a mechanism for detecting a residual ink amount or existence/absence of ink in the ink tank.
As an example of printing apparatus having an ink-existence detection apparatus of this type, Japanese Patent Publication Laid Open No. 8-112907 discloses an ink-jet printing apparatus which detects existence/absence of residual ink in an ink tank having a negative-pressure generating member of, e.g., absorbent material, foaming material and the like, by transmitting light through a part of light-transmitting wall surface of the ink tank and detecting changes in optical reflectivity in the boundary portion between the wall surface of the ink tank and the negative-pressure generating member.
Further, Japanese Patent Publication Laid Open No. 7-218321 discloses an ink tank integrating an optical ink detection portion, formed with a light-transmitting member being the same material as that of the ink tank, where the surface contacting ink has a predetermined angle with respect to a detection light path.
Further, Japanese Patent Publication Laid Open No. 9-174877 discloses a detection system which detects existence of ink tank and the level of ink in the ink tank.
Further, Japanese Patent Publication Laid Open No. 9-29989 discloses an ink-jet printing apparatus which detects existence/absence of ink and existence/absence of ink tank by using a single photosensor having a light-emitting device and a photoreception device.
Further, Japanese Patent Publication Laid Open No. 7-89090 discloses an apparatus for detecting existence/absence of liquid contained in a liquid container comprising: a negative-pressure generating member accommodating chamber accommodating a negative-pressure generating member and having a liquid supply orifice and an atmospheric-air communicating portion; and a liquid containing chamber having a communication portion to communicate with the negative-pressure generating member accommodating chamber, and forming substantially closed space.
Next, a conventional ink existence/absence detection mechanism using a light-transmitting prism will be described with reference to FIG. 36. FIG. 36 shows the positional relation among a light-transmitting type prism provided on the bottom surface of an ink tank, a light emitting device which irradiates the prism with light, and a photoreception device which receives the light.
As shown in FIG. 36, a prism 1060 is integrally molded with a bottom surface 1061 of the ink tank. Light from a light emitting device 1062 in an external lower position with respect to the ink tank enters the prism 1060.
If there is sufficient ink in the ink tank, the incident light from the light emitting device 1062 passes through an optical path {circle around (1)}→an optical path {circle around (2)}′, then is absorbed in the ink and never returns to the photoreception device 1063. On the other hand, if the ink in the ink tank is consumed and is exhausted, the light from the light emitting device 1062 is reflected by a slope of the prism 1060, and through the optical path {circle around (1)}→the optical path {circle around (2)}→an optical path {circle around (3)}, returns to the photoreception device 1063, as shown in FIG. 36.
In this manner, the existence/absence of ink is determined based on whether or not the light emitted from the light emitting device 1062 returns to the photoreception device 1063. Note that the light emitting device 1062 and the photoreception device 1063 are provided on the printing apparatus main body side.
The above-described ink existence/absence detection mechanism provides a rational method to detect the level of ink or existence/absence of ink in the ink tank at a low cost.
Next, the outline of the structure of the conventional ink-jet printing apparatus, the ink tank and a tank holder holding the ink tank will be described.
FIG. 37 is a perspective view showing a conventional general ink-jet printing apparatus.
In the ink-jet printing apparatus in FIG. 37, a lead screw 2104 and a guide shaft 2105 parallel to each other are provided in a casing. A carriage 2101 is attached to the lead screw 2104 and the guide shaft 2105 such that the carriage is movable in parallel to the lead screw 2104 and the guide shaft 2105. The carriage 2101 moves parallel with the lead screw and the guide shaft by rotation of the lead screw 2104 by a carriage motor (not shown).
The carriage 2101 holds an ink-jet head cartridge having an ink-jet printhead 2102 (hereinafter referred to as “printhead”) to be described with reference to FIGS. 38A and 38B. A paper-pressing plate 2109 is provided along the moving direction of the printhead 2102.
Further, the ink-jet printing apparatus comprises a paper feed roller 2107 to convey a print sheet 2106 as a print medium toward a printing area of the printhead 2102, and a paper discharge roller 2108 to discharge the print sheet 2106 on which printing has been performed by the printhead 2102. The paper feed roller 2107 and the paper discharge roller 2108 are rotated by a conveyance motor (not shown).
As ink discharged from the printhead 2102 is attached to the print sheet 2106 opposite to a discharge orifice surface of the printhead 2102, a print image is formed on the surface of the print sheet 2106. In connection with the printing by the printhead 2102 on the print sheet 2106, the print sheet 2106 is discharged to the outside the ink-jet printing apparatus by the paper feed roller 2107 and the paper discharge roller 2108 rotated by a conveyance motor, and the paper pressing plate 2109.
FIGS. 38A and 38B are diagrams for explaining an ink-jet head cartridge mounted on the carriage 2101 as shown in FIG. 37. FIG. 38A is a perspective view showing the ink-jet head cartridge mounted on the carriage 2101. FIG. 38B is a perspective view showing a state where the ink tank is removed from a tank holder in the ink-jet head cartridge in FIG. 38A.
As shown in FIGS. 38A and 38B, an ink-jet head cartridge 2301 mounted on the carriage 2101 comprises a tank holder 2103 having the printhead 2102 and ink tanks 2111 to 2114 detachably provided on the tank holder 2103. The ink tank 2111 contains black ink; the ink tank 2112, yellow ink; the ink tank 2113, magenta ink; and the ink tank 2114, cyan ink. As the ink tanks 2111 to 2114 are respectively detachable with respect to the tank holder 2103, and respectively exchangeable with a new ink tank, the running cost in printing by the ink-jet printing apparatus can be reduced.
The ink tanks 2111 to 2114, respectively containing corresponding color ink, respectively have an ink supply orifice to supply the ink to the printhead 2102. For example, the ink tank 2111 has an ink supply orifice 2211. In a state where the ink tank 2111 is attached to the tank holder 2103, the black ink in the ink tank 2111 is supplied via the ink supply orifice 2211 to the printhead 2102.
FIG. 39 is a cross-sectional view of the tank holder 2103 and the printhead 2102 as shown in FIGS. 38A and 38B. As shown in FIG. 39, the upper surface of a box-shaped tank holder 2103 is opened, and the printhead 2102 is provided on one side surface of the tank holder 2103. In the printhead 2102, a silicon substrate 2201 is supported by a base plate 2205. Heaters as electrothermal transducers or the like to generate thermal energy utilized for ink discharge are formed on the silicon substrate 2201.
Further, the printhead 2102 has a joint 2204 to be connected to the ink supply orifice of an ink tank when the ink tank is attached to the tank holder 2103. The joint 2204 has an ink channel 2206 extending toward the silicon substrate 2201.
The flow of ink in the ink-jet head cartridge having the above construction will be described with reference to the ink tank 2111 for black ink. The ink in the ink tank 2111 is supplied via the ink supply orifice 2211 of the ink tank 2111 and the joint 2204 into the printhead 2102. The ink supplied to the printhead 2102 is supplied through the ink channel 2206 to the silicon substrate 2201, and the supplied ink is discharged toward a print sheet as a print medium by thermal energy generated by the heaters on the silicon substrate 2201.
FIGS. 40A to 40C are diagrams for explaining the ink tank 2111 as shown in FIGS. 38A and 38B. FIG. 40A is a perspective view showing the ink tank 2111 and a second latch 2132. FIG. 40B is a perspective view showing the ink tank 2111 and a movable lever 2130. FIG. 40C is a cross-sectional view of the ink tank 2111.
As shown in FIGS. 40A and 40B, the movable lever 2130 having a first latch 2131 is provided on one side surface of the ink tank 2111, and the second latch 2132 is provided on another side surface of the ink tank 2111. When the ink tank 2111 is attached to the tank holder 2103, the first latch 2131 and the second latch 2132 engage with a first hole 2241 and a second hole 2242 (See FIG. 39) formed in the tank holder 2103. By this arrangement, the ink tank 2111 is fixed on the tank holder 2103. The ink tank 2111 has the ink supply orifice 2211 having a projecting cylindrical shape on its lower surface.
Further, as shown in FIG. 40C, a joint member 2137 to be in contact with liquid is filled in the ink supply orifice 2211. When the ink tank 2111 is attached to the tank holder 2103, the ink in the ink tank is supplied from the ink supply orifice 2211 through the joint member 2137 to the printhead 2102. Further, a prism 1060 used for detecting residual ink in the ink tank is provided on the inner bottom surface of the ink tank 2111.
Next, a procedure of setting the ink tank 2111 to the tank holder 2103 of the ink-jet head cartridge 2301 will be described with reference to FIGS. 41A to 41C.
First, as shown in FIG. 41A, the surface having the ink supply orifice 2211 of the ink tank 2111 is faced to the upper surface of the tank holder 2103, and the second latch 2132 of the ink tank 2111 is tilted downward while the ink tank 2111 is inserted into the tank holder 2103.
Next, as shown in FIG. 41B, as the ink tank is inserted along a slope of the tank holder 2103 on the right side in FIG. 41B, the second latch 2132 of the ink tank 2111 engages with the second hole 2242 of the tank holder 2103.
Further, as shown in FIG. 41C, as the ink tank 2111 is pushed into the tank holder 2103, the movable lever 2103 is distorted inwardly, then the first latch 2131 engages with the first hole 2341 of the tank holder 2103, thus the ink tank 2111 is fixed to the tank holder 2103.
In this state, the ink contained in the ink tank is introduced via the joint-member 2137 of the ink supply orifice 2211 to the printhead 2102, and discharged from a discharge orifice (not shown) by energy generated by the electrothermal transducer.
Note that when the ink tank 2111 is removed, the movable lever 2130 is distorted inwardly and the first latch 2131 is pulled out of the first hole 2241 of the tank holder 2103. Thus, the ink tank 2111 can be easily removed from the tank holder 2103.
Further, as shown in FIGS. 42A and 42B, a sensor 2303 is provided for each color ink tank under the ink-jet head cartridge 2301 having the above-described construction. When the ink tank 2111, for example, is attached to the tank holder 2103, the sensor in cooperation with the prism 1060 on the inner bottom surface of the ink tank, detects residual ink within the tank.
However, the above-described conventional art has the following problems.    (1) To improve the detection precision of the ink existence/absence detecting mechanism by precisely obtaining the positional relation between the prism in the ink tank and the optical unit having the light emitting device and the photoreception device, it is necessary to greatly improve the precision of attachment of respective parts and units, such as the precision of attachment of ink tank to the tank holder or carriage, the precision of attachment of printhead to the carriage, the precision of attachment of the carriage to the printing apparatus main body, the precision of the attachment of the optical unit to the printing apparatus main body. Accordingly, it is necessary to improve machining precision with respect to the parts and to improve the precision of assembly line. This increases the production cost.    (2) In a case where two printheads to discharge different types of ink are set in positions shifted from each other in a print-medium conveyance direction within one printing apparatus, to print a higher quality image and/or perform color printing, two ink tanks to supply ink to the respective printheads are provided in different positions. When existence/absence of ink is detected in the position-shifted ink tanks, two optical units must be provided in the printing apparatus. This also increases the production cost.    (3) In a case where a single type of ink tank is commonly used by plural types of printing apparatuses, as the position of the prism in the ink tank is fixed, the positions of the light emitting device and the photoreception devices provided on the printing apparatus side are uniquely determined. This greatly limits freedom in design of the printing apparatus.
Further, in the above-described conventional art, if the ink viscosity has increased in a low-temperature environment or the like or if the ink tank is exposed in a severe environment such as a high-temperature environment or a low-temperature environment where the ink is easily attached to the inner wall surface of the tank, even if the ink in the ink tank is almost used, a small amount of ink 1067 may remain on the surface of the prism, as shown in FIG. 43.
In this case, it is assumed that there is no ink, light emitted from the light emitting device 1062 must be reflected by a slope of the prism 1060, and must be returned through optical path {circle around (1)}→{circle around (2)}→{circle around (3)} to the photoreception device 1063. However, as the ink 1067 remains on the surface of the prism, the light emitted from the light emitting device 1062 enters the ink tank through optical paths {circle around (1)}→{circle around (2)}′, and as a result, the amount of light returned to the photoreception device 1063 is less than an expected amount.
Accordingly, although the ink is exhausted in the ink tank, it is determined that the ink still remains in the ink tank.
Further, in the above conventional art, as shown in FIG. 42B, since the ink tank is attached and fixed to the tank holder 2103 only by engaging the first latch 2131 and the second latch 2132 of the ink tank 2111 with the first hole 2241 and the second hole 2242 of the tank holder 2103, the positional precision of the ink tank in the tank holder 2103 is lowered. Accordingly, in detection of residual ink in the tank, the detection precision might be degraded depending on the construction of the sensor and that of the prism. In this case, before the ink within the tank is not fully used, a user is advised to exchange the ink tank for new one.